waste of money vs wastefulness

waste of money and wastefulness both are nouns.

Word	Noun	Adjective	Verb	Adverb
waste of money	Yes	No	No	No
wastefulness	Yes	No	No	No

As nouns, wastefulness is a hypernym of waste of money; that is, wastefulness is a word with a broader meaning than waste of money:

waste of money: money spent for inadequate return
wastefulness: useless or profitless activity; using or expending or consuming thoughtlessly or carelessly

Other hypernyms of waste of money include dissipation, waste.

waste of money (noun)	wastefulness (noun)
money spent for inadequate return	useless or profitless activity; using or expending or consuming thoughtlessly or carelessly
	the trait of wasting resources